Support is requested for the acquisition of a modern, extended mass range mass spectrometer, equipped with fast atom bombardment capabilities, and suitable for the analysis of trace amounts of polar, non-volative and/or thermally labile compounds of biological origin. The proposed mass spectrometer will be used in support of NIH-funded research projects at the University of Washington which require structural characterization of a variety of compound types, including peptides from protein hydrolysates, drug-peptide covalent adducts, coenzyme A esters of potentially toxic drug metabolites, mutagenic agents present as environmental contaminants and xenobiotic-modified nucleic acids. Each of these projects has an absolute requirement for "soft" ionization capabilities and for an instrument with an operating mass range, at high sensitivity, in the 1,000-3,000 Dalton region. No such mass spectrometry facilities are currently available at the University of Washington.